1. Field of the Invention
This invention relates generally to patterned perpendicular magnetic recording media, such as disks for use in magnetic recording hard disk drives, and more particularly to patterned disks wherein the data bits are stored on elevated magnetic data islands isolated from one another by recessed nonmagnetic regions.
2. Description of the Related Art
Magnetic recording hard disk drives with patterned magnetic recording media have been proposed to increase data density. In patterned media the magnetic recording layer on the disk is patterned into small isolated data islands arranged in concentric data tracks. Patterned-media disks may be longitudinal magnetic recording disks, wherein the magnetization directions are parallel to or in the plane of the recording layer, or perpendicular magnetic recording disks, wherein the magnetization directions are perpendicular to or out-of-the-plane of the recording layer. To produce the required magnetic isolation of the patterned data islands, the magnetic moment of the spaces between the islands must be destroyed or substantially reduced to render these spaces essentially nonmagnetic. In one type of patterned media, the data islands are elevated, spaced-apart pillars that extend above the disk substrate surface to define troughs or trenches on the substrate surface between the pillars. This type of patterned media is of interest because substrates with the pre-etched pattern of pillars and trenches can be produced with relatively low-cost, high volume processes such as lithography and nanoimprinting. The magnetic recording layer material is then deposited over the entire surface of the pre-etched substrate to cover both the ends of the pillars and the trenches. It was believed that because the trenches were recessed they would be far enough from the read/write head to not adversely affect reading or writing. This type of patterned media is described in U.S. Pat. No. 6,440,520, and by Moritz et al., “Patterned Media Made From Pre-Etched Wafers: A Promising Route Toward Ultrahigh-Density Magnetic Recording”, IEEE Transactions on Magnetics, Vol. 38, No. 4, July 2002, pp. 1731-1736. This type of patterned media with perpendicular magnetization on the pillar ends is believed to provide opportunity for ultra-high density magnetic recording. However, it has been discovered that the magnetic material in the trenches creates noise in the readback signal and also adversely affects writing the individual data bits (i.e., magnetizing the recording material on the pillar ends).
Pending application Ser. No. 11/558,846 filed Nov. 10, 2006, and assigned to the same assignee as this application, describes a patterned perpendicular magnetic recording medium that allows use of a pre-etched substrate with patterned pillars. The substrate has material in the trenches that diffuses into the magnetic recording layer material in the trenches during an annealing process. The diffusion material chemically reacts or interdiffuses with one or more of the elements in the recording layer material to render the trenches nonmagnetic or with significantly reduced magnetic moment. The time and temperature of the annealing process needs to be carefully controlled to assure there is no adverse effect on the recording layer material on the pillars.
What is needed is a patterned perpendicular magnetic recording medium with trenches rendered nonmagnetic by chemical reaction of diffusion material and recording layer material, and a manufacturing process that prevents any chemical reaction of the diffusion material with the recording layer material on the pillars.